I didn't say it wasn't a problem - if I could wave a magic wand and get rid of the concept of null in Java I would. That isn't what we're discussing though - you said, "The biggest thing missing in Java is an answer for the billion-dollar mistake [- NPEs]". I've provided what I consider to be at least a partial answer. If you care about avoiding NPEs in Java, it's a pretty good solution.

Realistically, null is so fundamental to the Java language that removing it would arguably result in a different language entirely. Certainly all existing java codebases would have to be refactored. The same goes for exceptions. That's obviously not an option when one of your primary selling points is backwards compatibility, so I'm not really sure what kind of solution you're looking for here.

The answer to your SO link notwithstanding, I would argue the @lombok.NonNull is at least one of the best options, as it actually generates a null check that is executed at runtime. This makes it more powerful than most of the other solutions.